watchdog monitoring file for changes

I have a need to watch a log file for changes. After looking through stackoverflow questions, I see people recommending watchdog. So I’m trying to test, and am not sure where to add the code for when files change:

import time
from watchdog.observers import Observer
from watchdog.events import LoggingEventHandler

if __name__ == "__main__":
    event_handler = LoggingEventHandler()
    observer = Observer()
    observer.schedule(event_handler, path='.', recursive=False)
    observer.start()
    try:
        while True:
            time.sleep(1)
        else:
            print "got it"
    except KeyboardInterrupt:
        observer.stop()
    observer.join()

Where do I add the “got it” — in the while loop if the files have been added/changed?

Answer

Instead of LoggingEventHandler define your handler:

#!/usr/bin/python
import time
from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler


class MyHandler(FileSystemEventHandler):
    def on_modified(self, event):
        print(f'event type: {event.event_type}  path : {event.src_path}')


if __name__ == "__main__":
    event_handler = MyHandler()
    observer = Observer()
    observer.schedule(event_handler, path='/data/', recursive=False)
    observer.start()

    try:
        while True:
            time.sleep(1)
    except KeyboardInterrupt:
        observer.stop()
    observer.join()

on_modified is called when a file or directory is modified.